Stem cells are pluripotent or totipotent cells that can differentiate in vivo or in vitro into many or all cell lineages. Due to their pluripotency, embryonic stem (ES) cells are believed to hold a great promise for treating degenerative or inherited diseases. Yet, ethical considerations have hampered the use of human ES cells. Stem cells of a non-embryonic origin would circumvent this obstacle. Thus, there is a need for non-embryonic stem cells.